Engine bearing

ABSTRACT

A journal bearing has a lining of bearing metal applied to a steel backing. The surface of the lining is laser peen hardened to locally increase the hardness and the seizure resistance of the lining. The underlying core of the lining is unaffected and maintains good conformability of the lining. The overall lining thus possesses both good seizure resistance and conformability.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] This invention relates generally to journal or engine bearingsfor internal combustion engines, and more particularly to theconstruction of linings for journal bearings.

[0003] 2. Related Art

[0004] Sliding-type journal or engine bearings are typically used ininternal combustion engine applications for journaling a shaft of theengine. Typical engine bearings have an arcuate steel backing onto whichone or more layers of relatively softer bearing metal is applied.

[0005] The steel backing provides structural rigidity to the bearingwhereas the applied bearing layer or layers provide a low frictionsliding surface that must exhibit a combination of seeminglyincompatible properties of acceptable wear and fatigue resistance, andacceptable conformability and seizure-resistance. The first twoproperties call for a hard, strong bearing material, whereasconformability and seizure resistance call for a softer material oflesser strength. It is generally accepted that no one material cansatisfy all criteria, since a material cannot be both hard and soft.Accordingly, the current practice is to select a material, or multiplelayer materials, that compromise between the competing properties.However, the demand for ever-increasing performance of engine bearingscontinues to challenge ability to provide a suitable “compromise”bearing material at an acceptable cost. Modern bearings and those of thefuture require ever-increasing wear and fatigue resistance propertieswithout sacrificing the conformability of the bearings. As the demandsof these competing properties get driven further apart, a suitablecompromise material(s) is becoming more difficult to attain.

[0006] It is an object of the present invention to overcome or greatlyminimize the foregoing limitations of prior engine bearings.

SUMMARY OF THE INVENTION

[0007] An engine bearing for an internal combustion engine has a liningwith a hardened surface layer providing the journal bearing with anextended life in use. The bearing has an arcuate backing comprised of afirst material having an outer surface and an inner surface. A liningcomprised of a second material different from the first material isfixed to the inner surface of the backing. According to the invention,the lining is laser peened (also known as “laser shock hardened”) toimpart compressive residual stresses in a surface region to produce ahardened skin with enhanced fatigue and wear resistance while anunderlying core of the lining is unaffected and possesses goodconformability and seizure resistance.

[0008] One advantage of the present invention is that a journal typebearing is provided having an extended life in use.

[0009] Another advantage of the invention is that a greater variety ofbearing metals are available that can satisfy the competing propertiesof fatigue resistance and conformability

THE DRAWINGS

[0010] These and other features and advantages of the present inventionwill become more readily appreciated when considered in connection withthe following detailed description and appended drawings, wherein:

[0011]FIG. 1 is a prospective view of a presently preferred embodimentof a journal bearing embodying the present invention;

[0012]FIG. 2 is a cross sectional view taken along the line 2-2 of FIG.1; and

[0013]FIG. 3 is an enlarged and magnified plan view of one-half of thejournal bearing of FIG. 1.

DETAILED DESCRIPTION

[0014] A presently preferred embodiment of a journal bearing constructedaccording to the present invention is shown generally at 10 in FIGS.1-3. The journal bearing 10 has a backing plate 12 and a lining 14. Thebacking plate 12 provides rigidity to the journal bearing 10.

[0015] The backing plate 12 is formed of a first material, preferablysteel, and has an outer arcuate convex surface 18 and an inner arcuateconcave surface 20.

[0016] The lining 14 is formed from a second lining material differentthan that of the backing plate material. Preferably, the lining materialcomprises either an aluminum-based or copper-based alloy material. Thelining 14 has a first side 22 and a second side 24. The first side 22 ofthe lining 14 is fixed to the inner surface 20 of the backing plate 12.The second side 24 of the lining 14 defines an inner arcuate bearingsurface 16 that is spaced radially inwardly from the backing plate 12.

[0017] To improve the strength characteristics of the bearing surface16, the second side 24 of the lining 14 is treated by laser peening orlaser shock peening, which is known per se for the treatment ofmaterials generally, but not known in connection with engine bearings toincrease fatigue resistance while preserving conformability and seizureresistance of a bearing lining material. The laser peened treatmentinduces residual compressive stresses which serve to locally hardenouter layer region 26 of the lining 14. The hardened layer 26 improvesthe fatigue resistance of the bearing surface 16 by inhibiting crackinitiation and propagation within and through the bearing surface 16. Asa result, the service life of the journal bearing 10 is extended.

[0018] The laser surface peening process subjects the second side 24 ofthe lining 14 to a laser pulse with a power density of approximately 1gigawatt/cm² with an interaction time of approximately 1 microsecond.

[0019] The lining 14 has a non-laser peened layer or core 28 between thehardened layer 26 and the backing 12. Typically, upon laser peening thesecond side 24, the hardened layer 26 takes on a hardness value ranginganywhere between 0-5 points on the Vickers scale greater than thehardness of the core 28, though this range can be increased depending onthe laser surface peening parameters. Though the bearing surface 16 isharder than the core layer 28 of the lining 14, the bearing surface 16and core 28 retain a combined desirable level of conformability, withthe core 28 exhibiting greater conformability than that of the hardenedlayer 26.

[0020] The hardened layer 26 preferably extends to a depth of about 20to 50 micrometers below the surface 16. As such, the conformability ofthe core 28, and thus the overall lining is largely unaffected, as theconformability has been formed to be influenced primarily within a depthof ¼-½ mm below the bearing surface 16. Conformability of the journalbearing is particularly beneficial in applications that are prone tomisalignment of the shaft relative to the journal bearing, thus causingan effect commonly referred to as “edge loading.” In addition, anyimperfections in machining of the shaft, such as a crank shaft in aninternal combustion engine, can reduce the useful life of the journalbearing 10 if adequate conformability is not provided in the lining 14of the journal bearing 10.

[0021] In journal bearing applications it is common for contaminants ordebris to come in contact with the journal bearing 10. Thus, it isdesirable to provide journal bearings that can operate in the presencesof contaminants or debris without negatively impacting the useful lifeof the journal bearings. The journal bearing 10, having a bearingsurface 16 and a hardened layer 26 does not impair the embedabilityproperties of the journal bearing 10 to retain contamination or debriswithin the bearing surface 16.

[0022] According to a further aspect of the invention, the laser peeningmay be advantageously controlled to develop a particular texturedsurface 30 of the hardened layer 26. For example, as best shown in FIG.3, the surface texturing 30 provides for circumferentially extendinggrooves, represented here as a plurality of generally parallel grooves,promoting the retention of lubrication and enhanced hydrodynamic actionon the bearing surface 16 of the journal bearing 10. The surfacetexturing 30 is formed during the laser surface peening process bydirecting the shock waves to the desired location on the second side 24of the lining 14. While a grooved texture is illustrated by way ofexample, the invention contemplates other textures, for example, groovesin other directions, such as axial grooves.

[0023] Obviously, many modifications and variations of the presentinvention are possible in light of the above teachings. It is,therefore, to be understood that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed. The invention is defined by the claims.

What is claimed is:
 1. An engine bearing for an internal combustionengine, comprising: an arcuate metal backing plate; a lining of bearingmetal different than that of the backing plate applied to said backingplate and presenting an inner arcuate surface; and said inner arcuatesurface of said lining being treated by laser peening to inducecompressive residual stresses in said inner arcuate surface to define alocally hardened surface layer of said lining backed by a core of saidlining, wherein said hardened surface layer has a hardness and fatiguestrength exceeding that of said core, and said core is relatively moreconformable than that of said hardened surface layer.
 2. The enginebearing of claim 1 wherein said backing plate is fabricated of steel. 3.The engine bearing of claim 1 wherein said bearing metal comprises analuminum-based alloy.
 4. The engine bearing of claim 1 wherein said coreextends from said hardened layer to said backing plate.
 5. The enginebearing of claim 1 further comprising a textured surface on saidhardened surface layer.
 6. The engine bearing of claim 5 wherein saidtextured surface comprises circumferential grooves.
 7. The enginebearing of claim 1 wherein said hardened surface layer extends about 20to 50 micrometers below said inner arcuate surface.
 8. The enginebearing of claim 1 wherein said hardened surface layer has a hardnessabout 0 to 5 points greater on a Vickers scale than said core of saidlining.
 9. The engine bearing of claim 1 wherein said core has ahardness less than both said arcuate metal backing plate and saidhardened surface layer.
 10. A method of manufacturing an engine bearingfor an internal combustion engine, comprising: forming an arcuate metalbacking plate; forming a lining of bearing metal different than that ofthe backing plate on the backing plate defining an inner arcuatesurface; and imparting compressive residual stresses within a layer ofthe lining extending from the inner arcuate surface toward the arcuatemetal backing plate.
 11. The method of manufacturing an engine bearingof claim 10 further providing a laser peening operation for impartingthe compressive residual stresses within the lining.
 12. The method ofmanufacturing an engine bearing of claim 10 further constructing ahardened surface layer and a core within the lining upon impartingcompressive residual stresses within the lining.
 13. The method ofmanufacturing an engine bearing of claim 12 wherein the hardened surfacelayer is constructed having a hardness about 0 to 5 points greater on aVickers scale than the core of the lining.
 14. The method ofmanufacturing an engine bearing of claim 12 wherein the hardened surfacelayer is constructed extending about 20 to 50 micrometers below theinner arcuate surface.
 15. The method of manufacturing an engine bearingof claim 12 wherein the core is constructed having a hardness less thanboth the arcuate metal backing plate and the hardened surface layer. 16.The method of manufacturing an engine bearing of claim 10 furthercomprising constructing a textured surface on the inner arcuate surface.17. The method of manufacturing an engine bearing of claim 16 whereinthe textured surface is constructed as circumferential grooves.
 18. Themethod of manufacturing an engine bearing of claim 10 wherein steel isprovided in forming the arcuate metal backing plate.
 19. The method ofmanufacturing an engine bearing of claim 10 wherein an aluminum-basedmaterial is provided in forming the lining.